perf: Evaluate parallel code review and acceptance review after passed quality gate

[trsdn]

Summary

Evaluate a low-risk way to run automated code review and acceptance review concurrently once an issue has passed the quality gate and developer editing is complete.

Why

These phases are currently serialized after quality gate success, even though both operate on the same frozen diff and primarily read/analyze rather than modify branches.

Constraints

• Do not parallelize developer implementation across issues.
• Preserve deterministic final behavior when either review requests changes.
• Avoid duplicate or conflicting feedback loops.

Acceptance criteria

• Clear design for how review outcomes are aggregated.
• If one or both reviews request changes, the developer receives one deterministic follow-up path.
• If concurrency is rejected as too risky, document why and close the issue with evidence.
• Tests cover the chosen orchestration behavior.